// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
 *******************************************************************************
 * Copyright (C) 1996-2014, International Business Machines Corporation and    *
 * others. All Rights Reserved.                                                *
 *******************************************************************************
 */

package com.ibm.icu.util;

import com.ibm.icu.util.ULocale.Category;
import java.util.BitSet;
import java.util.Date;
import java.util.Locale;

/**
 * <code>PersianCalendar</code> is a subclass of <code>Calendar</code> that that implements the
 * Persian calendar. It is used as the main civil calendar in Iran and Afghanistan, and by Iranians
 * and Afghans worldwide.
 *
 * <p>The Persian calendar is solar, and is similar to the Gregorian calendar in various ways,
 * except its leap year rule, which is determined astronomically. The Persian year starts around the
 * March equinox.
 *
 * <p>The modern Persian calendar (used in Iran since 1925 CE and in Afghanistan since 1957 CE), has
 * the lengths of the months fixed. The first six months are 31 days each, the next five months are
 * 30 days each, and the final month is 29 days in non-leap years and 30 days in leap ones.
 * Historically, the lengths of the month differed in different years, but they were finally fixed
 * at the times mentioned above. Partial information is available about the historical lengths.
 *
 * <p>The official rule for determination of the beginning of the Persian year is locale dependent,
 * but at the same time, it has not specified a locale. Iranians around the world traditionally
 * follow the calendar authorities of Iran, which haven't officially specified the locale. Some
 * calendarists use some point in Tehran as the locale, while others have tried the more neutral
 * 52.5 degrees east meridian. It is not clear which locale should be used for the Persian calendar
 * of Afghanistan, but it is expected that for about one year in every twenty-four years, the Afghan
 * calendar may become different from the Iranian one.
 *
 * <p>The exact locale to be used for the Iranian calendar starts to make a difference at around
 * 2090 CE. The specific arithmetic method implemented here, commonly known as the 33-year cycle
 * rule, matches the astronomical calendar at least for the whole period that the calendar has been
 * both well-defined and official, from 1925 to around 2090 CE. The other commonly known algorithm,
 * the 2820-year cycle, has been incorrectly designed to follow the tropical year instead of the
 * spring equinoctial year, and fails to match the astronomical one as early as 2025 CE.
 *
 * <p>This class should not be subclassed.
 *
 * <p>PersianCalendar usually should be instantiated using {@link
 * com.ibm.icu.util.Calendar#getInstance(ULocale)} passing in a <code>ULocale</code> with the tag
 * <code>"@calendar=persian"</code>.
 *
 * @see com.ibm.icu.util.GregorianCalendar
 * @see com.ibm.icu.util.Calendar
 * @author Roozbeh Pournader
 * @internal
 * @deprecated This API is ICU internal only.
 */
@Deprecated
public class PersianCalendar extends Calendar {
    private static final long serialVersionUID = -6727306982975111643L;

    // -------------------------------------------------------------------------
    // Constants...
    // -------------------------------------------------------------------------

    private static final int[][] MONTH_COUNT = {
        // len len2   st
        {31, 31, 0}, // Farvardin
        {31, 31, 31}, // Ordibehesht
        {31, 31, 62}, // Khordad
        {31, 31, 93}, // Tir
        {31, 31, 124}, // Mordad
        {31, 31, 155}, // Shahrivar
        {30, 30, 186}, // Mehr
        {30, 30, 216}, // Aban
        {30, 30, 246}, // Azar
        {30, 30, 276}, // Dey
        {30, 30, 306}, // Bahman
        {29, 30, 336} // Esfand
        // len  length of month
        // len2 length of month in a leap year
        // st   days in year before start of month
    };

    private static final int PERSIAN_EPOCH = 1948320;

    private static final class NonLeapYears {
        private static final int NON_LEAP_YEARS[] = {
            1502, 1601, 1634, 1667, 1700, 1733, 1766, 1799, 1832, 1865, 1898, 1931, 1964, 1997,
                    2030, 2059,
            2063, 2096, 2129, 2158, 2162, 2191, 2195, 2224, 2228, 2257, 2261, 2290, 2294, 2323,
                    2327, 2356,
            2360, 2389, 2393, 2422, 2426, 2455, 2459, 2488, 2492, 2521, 2525, 2554, 2558, 2587,
                    2591, 2620,
            2624, 2653, 2657, 2686, 2690, 2719, 2723, 2748, 2752, 2756, 2781, 2785, 2789, 2818,
                    2822, 2847,
            2851, 2855, 2880, 2884, 2888, 2913, 2917, 2921, 2946, 2950, 2954, 2979, 2983, 2987,
        };
        private int minYear = NON_LEAP_YEARS[0];
        private int maxYear = NON_LEAP_YEARS[NON_LEAP_YEARS.length - 1];
        private BitSet offsetYears;

        public NonLeapYears() {
            offsetYears = new BitSet(maxYear - minYear + 1);
            for (int nonLeap : NON_LEAP_YEARS) {
                offsetYears.set(nonLeap - minYear);
            }
        }

        public boolean contains(int year) {
            return minYear <= year && year <= maxYear && offsetYears.get(year - minYear);
        }
    }

    private static NonLeapYears LEAP_CORRECTION = new NonLeapYears();

    // -------------------------------------------------------------------------
    // Constructors...
    // -------------------------------------------------------------------------

    /**
     * Constructs a default <code>PersianCalendar</code> using the current time in the default time
     * zone with the default <code>FORMAT</code> locale.
     *
     * @see Category#FORMAT
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Deprecated
    public PersianCalendar() {
        this(TimeZone.getDefault(), ULocale.getDefault(Category.FORMAT));
    }

    /**
     * Constructs a <code>PersianCalendar</code> based on the current time in the given time zone
     * with the default <code>FORMAT</code> locale.
     *
     * @param zone the given time zone.
     * @see Category#FORMAT
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Deprecated
    public PersianCalendar(TimeZone zone) {
        this(zone, ULocale.getDefault(Category.FORMAT));
    }

    /**
     * Constructs a <code>PersianCalendar</code> based on the current time in the default time zone
     * with the given locale.
     *
     * @param aLocale the given locale.
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Deprecated
    public PersianCalendar(Locale aLocale) {
        this(TimeZone.forLocaleOrDefault(aLocale), aLocale);
    }

    /**
     * Constructs a <code>PersianCalendar</code> based on the current time in the default time zone
     * with the given locale.
     *
     * @param locale the given ulocale.
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Deprecated
    public PersianCalendar(ULocale locale) {
        this(TimeZone.forULocaleOrDefault(locale), locale);
    }

    /**
     * Constructs a <code>PersianCalendar</code> based on the current time in the given time zone
     * with the given locale.
     *
     * @param zone the given time zone.
     * @param aLocale the given locale.
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Deprecated
    public PersianCalendar(TimeZone zone, Locale aLocale) {
        super(zone, aLocale);
        setTimeInMillis(System.currentTimeMillis());
    }

    /**
     * Constructs a <code>PersianCalendar</code> based on the current time in the given time zone
     * with the given locale.
     *
     * @param zone the given time zone.
     * @param locale the given ulocale.
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Deprecated
    public PersianCalendar(TimeZone zone, ULocale locale) {
        super(zone, locale);
        setTimeInMillis(System.currentTimeMillis());
    }

    /**
     * Constructs a <code>PersianCalendar</code> with the given date set in the default time zone
     * with the default <code>FORMAT</code> locale.
     *
     * @param date The date to which the new calendar is set.
     * @see Category#FORMAT
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Deprecated
    public PersianCalendar(Date date) {
        super(TimeZone.getDefault(), ULocale.getDefault(Category.FORMAT));
        this.setTime(date);
    }

    /**
     * Constructs a <code>PersianCalendar</code> with the given date set in the default time zone
     * with the default <code>FORMAT</code> locale.
     *
     * @param year the value used to set the {@link #YEAR YEAR} time field in the calendar.
     * @param month the value used to set the {@link #MONTH MONTH} time field in the calendar. Note
     *     that the month value is 0-based. e.g., 0 for Farvardin.
     * @param date the value used to set the {@link #DATE DATE} time field in the calendar.
     * @see Category#FORMAT
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Deprecated
    public PersianCalendar(int year, int month, int date) {
        super(TimeZone.getDefault(), ULocale.getDefault(Category.FORMAT));
        this.set(Calendar.YEAR, year);
        this.set(Calendar.MONTH, month);
        this.set(Calendar.DATE, date);
    }

    /**
     * Constructs a <code>PersianCalendar</code> with the given date and time set for the default
     * time zone with the default <code>FORMAT</code> locale.
     *
     * @param year the value used to set the {@link #YEAR YEAR} time field in the calendar.
     * @param month the value used to set the {@link #MONTH MONTH} time field in the calendar. Note
     *     that the month value is 0-based. e.g., 0 for Farvardin.
     * @param date the value used to set the {@link #DATE DATE} time field in the calendar.
     * @param hour the value used to set the {@link #HOUR_OF_DAY HOUR_OF_DAY} time field in the
     *     calendar.
     * @param minute the value used to set the {@link #MINUTE MINUTE} time field in the calendar.
     * @param second the value used to set the {@link #SECOND SECOND} time field in the calendar.
     * @see Category#FORMAT
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Deprecated
    public PersianCalendar(int year, int month, int date, int hour, int minute, int second) {
        super(TimeZone.getDefault(), ULocale.getDefault(Category.FORMAT));
        this.set(Calendar.YEAR, year);
        this.set(Calendar.MONTH, month);
        this.set(Calendar.DATE, date);
        this.set(Calendar.HOUR_OF_DAY, hour);
        this.set(Calendar.MINUTE, minute);
        this.set(Calendar.SECOND, second);
    }

    // -------------------------------------------------------------------------
    // Minimum / Maximum access functions
    // -------------------------------------------------------------------------

    private static final int LIMITS[][] = {
        // Minimum  Greatest     Least   Maximum
        //           Minimum   Maximum
        {0, 0, 0, 0}, // ERA
        {-5000000, -5000000, 5000000, 5000000}, // YEAR
        {0, 0, 11, 11}, // MONTH
        {1, 1, 52, 53}, // WEEK_OF_YEAR
        {
            /*                                   */
        }, // WEEK_OF_MONTH
        {1, 1, 29, 31}, // DAY_OF_MONTH
        {1, 1, 365, 366}, // DAY_OF_YEAR
        {
            /*                                   */
        }, // DAY_OF_WEEK
        {-1, -1, 5, 5}, // DAY_OF_WEEK_IN_MONTH
        {
            /*                                   */
        }, // AM_PM
        {
            /*                                   */
        }, // HOUR
        {
            /*                                   */
        }, // HOUR_OF_DAY
        {
            /*                                   */
        }, // MINUTE
        {
            /*                                   */
        }, // SECOND
        {
            /*                                   */
        }, // MILLISECOND
        {
            /*                                   */
        }, // ZONE_OFFSET
        {
            /*                                   */
        }, // DST_OFFSET
        {-5000000, -5000000, 5000000, 5000000}, // YEAR_WOY
        {
            /*                                   */
        }, // DOW_LOCAL
        {-5000000, -5000000, 5000000, 5000000}, // EXTENDED_YEAR
        {
            /*                                   */
        }, // JULIAN_DAY
        {
            /*                                   */
        }, // MILLISECONDS_IN_DAY
        {
            /*                                   */
        }, // IS_LEAP_MONTH
        {0, 0, 11, 11}, // ORDINAL_MONTH
    };

    /**
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Override
    @Deprecated
    protected int handleGetLimit(int field, int limitType) {
        return LIMITS[field][limitType];
    }

    // -------------------------------------------------------------------------
    // Assorted calculation utilities
    //

    /** Determine whether a year is a leap year in the Persian calendar */
    private static final boolean isLeapYear(int year) {
        if (LEAP_CORRECTION.contains(year)) {
            return false;
        }
        if (LEAP_CORRECTION.contains(year - 1)) {
            return true;
        }
        int[] remainder = new int[1];
        floorDivide(25 * year + 11, 33, remainder);
        return remainder[0] < 8;
    }

    // ----------------------------------------------------------------------
    // Calendar framework
    // ----------------------------------------------------------------------

    /**
     * Return the length (in days) of the given month.
     *
     * @param extendedYear The Persian year
     * @param month The Persian month, 0-based
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Override
    @Deprecated
    protected int handleGetMonthLength(int extendedYear, int month) {
        // If the month is out of range, adjust it into range, and
        // modify the extended year value accordingly.
        if (month < 0 || month > 11) {
            int[] rem = new int[1];
            extendedYear += floorDivide(month, 12, rem);
            month = rem[0];
        }

        return MONTH_COUNT[month][isLeapYear(extendedYear) ? 1 : 0];
    }

    /**
     * Return the number of days in the given Persian year
     *
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Override
    @Deprecated
    protected int handleGetYearLength(int extendedYear) {
        return isLeapYear(extendedYear) ? 366 : 365;
    }

    // -------------------------------------------------------------------------
    // Functions for converting from field values to milliseconds....
    // -------------------------------------------------------------------------

    /**
     * Return JD of start of given month/year
     *
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Override
    @Deprecated
    protected int handleComputeMonthStart(int eyear, int month, boolean useMonth) {
        // If the month is out of range, adjust it into range, and
        // modify the extended year value accordingly.
        if (month < 0 || month > 11) {
            int[] rem = new int[1];
            eyear += floorDivide(month, 12, rem);
            month = rem[0];
        }

        long julianDay = PERSIAN_EPOCH - 1L + firstJulianOfYear(eyear);
        if (month != 0) {
            julianDay += MONTH_COUNT[month][2];
        }
        return (int) julianDay;
    }

    // -------------------------------------------------------------------------
    // Functions for converting from milliseconds to field values
    // -------------------------------------------------------------------------

    /**
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Override
    @Deprecated
    protected int handleGetExtendedYear() {
        int year;
        if (newerField(EXTENDED_YEAR, YEAR) == EXTENDED_YEAR) {
            year = internalGet(EXTENDED_YEAR, 1); // Default to year 1
        } else {
            year = internalGet(YEAR, 1); // Default to year 1
        }
        return year;
    }

    private static long firstJulianOfYear(int year) {
        long julianDay = 365L * (year - 1L) + floorDivide(8L * year + 21, 33L);
        if (LEAP_CORRECTION.contains(year - 1)) {
            julianDay--;
        }
        return julianDay;
    }

    /**
     * Override Calendar to compute several fields specific to the Persian calendar system. These
     * are:
     *
     * <ul>
     *   <li>ERA
     *   <li>YEAR
     *   <li>MONTH
     *   <li>DAY_OF_MONTH
     *   <li>DAY_OF_YEAR
     *   <li>EXTENDED_YEAR
     * </ul>
     *
     * The DAY_OF_WEEK and DOW_LOCAL fields are already set when this method is called.
     *
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Override
    @Deprecated
    protected void handleComputeFields(int julianDay) {
        int year, month, dayOfMonth, dayOfYear;

        long daysSinceEpoch = julianDay - PERSIAN_EPOCH;
        year = 1 + (int) floorDivide(33 * daysSinceEpoch + 3, 12053);

        long farvardin1 = firstJulianOfYear(year);

        dayOfYear = (int) (daysSinceEpoch - farvardin1); // 0-based
        if (dayOfYear == 365 && LEAP_CORRECTION.contains(year)) {
            year++;
            dayOfYear = 0;
        }
        if (dayOfYear < 216) { // Compute 0-based month
            month = dayOfYear / 31;
        } else {
            month = (dayOfYear - 6) / 30;
        }

        ++dayOfYear; // Make it 1-based now
        dayOfMonth = dayOfYear - MONTH_COUNT[month][2];

        internalSet(ERA, 0);
        internalSet(YEAR, year);
        internalSet(EXTENDED_YEAR, year);
        internalSet(MONTH, month);
        internalSet(ORDINAL_MONTH, month);
        internalSet(DAY_OF_MONTH, dayOfMonth);
        internalSet(DAY_OF_YEAR, dayOfYear);
    }

    private static final int PERSIAN_CALENDAR_RELATED_YEAR_DIFFERENCE = 622;

    /**
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Override
    @Deprecated
    protected final int getRelatedYearDifference() {
        return PERSIAN_CALENDAR_RELATED_YEAR_DIFFERENCE;
    }

    /**
     * {@inheritDoc}
     *
     * @internal
     * @deprecated This API is ICU internal only.
     */
    @Override
    @Deprecated
    public String getType() {
        return "persian";
    }
}
